With its Macondo well dead and few visitors on the coast during the offseason, BP has launched its biggest push yet to deep-clean the tourist beaches that were coated with crude during the worst of the Gulf oil spill. Machines are digging down into the sand to remove buried tar mats left from the Deepwater Horizon disaster.

The work is getting mixed reviews. Many are anxious to see the beaches cleaned as quickly as possible by whatever means are available. Others say BP may be making matters worse by bringing heavy equipment onto beaches and spreading the petroleum stain.

Some fear fresh environmental damage from the work itself, which can kill tiny creatures that live in the sand. Even BP acknowledges that fresh tar balls are still hitting the coast, meaning some of the work might be premature. Still, local officials have given the company a Jan. 1 deadline to be done.

The project began last month on Perdido Key at the Alabama-Florida line, and crews with sifting machines large and small are spreading out to the east and west. On a sunny day in mid-November, ground zero is the wide stretch of sand between the Gulf's crystal water and the Silver Beach condos in Orange Beach.

That's where Sue Rose has her ground-floor unit, and she was happy to see heavy machinery loading sand into a boxlike sifter just outside her door. The machine strains tons of dirty sand at a time through fine screens, and trucks then dump the cleaned sand back on to the beach. The refuse is taken to landfills.

A few miles away at Perdido Key, Fla., longtime resident Terry Hanners has his doubts. He sees what appears to be an ever-expanding oil stain on the beach and fears the once-white sand will remain its current brownish tint, which is close to the color of weak tea.

"They're just spreading it," said Hanners. "We have a stain that's going to stay with us a while."

An April 20 rig explosion killed 11 workers and led to more than 200 million gallons of oil spewing from BP's undersea well.

Seven months later, BP has settled on a multi-pronged cleaning approach at the urging of local leaders who fear a collapse of the region's tourist economy if all remnants of oil aren't gone from the beaches before tourists begin arriving in large numbers again next spring.

Thousands of workers roamed the coast with shovels and plastic bags all summer, picking up as much oil as they could as it washed in. There was no way to get all of it, though, and waves and tidal action soon buried large patches of tar and crude on beaches.

Faced with pressure to remove all the oil, BP sent assessment teams to beaches with augers to look for buried oil. Spots were marked and catalogued, and contractors worked with government officials on a plan for attacking the oil under the surface even as smaller amounts of oil continue to wash in.

Today, machines resembling agricultural harvesters move slowly along the beach digging about 18 inches below the surface in search of buried oil. Sand is lifted by a conveyor system and dumped onto screens; clean sand is expelled from the contraption, called a Sand Shark, while rust-colored tar balls, broken shells and other trash collect in a bin.

Workers are using a much larger cleaning system called a Powerscreen to scrub broader areas of beach. Dozers pile up sand, which a big machine with a bucket dumps into the sifter. Cleaned sand is ejected by one belt while tar and other material goes another way.

Workers have dug down about 30 inches so far to find oil, and officials say the dozers can dig as deep as needed to get the worst of the oil deposits. Different, gentler cleaning methods will be used in more delicate areas like Mississippi's coastal islands and the marshlands of Louisiana, the company says.

BP spokesman Ray Melick says the major work should be done by mid-February, before the weather turns warm and visitors begin heading back. Natural processes should finish cleaning tourist areas once the big machines have dug up all the oil they can.

"I think we'll get 99 percent of what's out there. There may be some little BB-sized tar balls that get left, but over time nature will take care of that on its own and it will just sort of dissolve back into the surface," he said.

Looking to speed up nature, the company also is pumping salt water on to the beach in some areas in an attempt to rinse away the oil residue and speed up the bleaching process, he said.

The work has raised concern among environmentalists who fear the heavy machinery will kill creatures that live on the beach or cause erosion problems as the natural lay of the land is disturbed. Marine scientist George Crozier says the work is doing some damage, like killing small ghost crabs that live in the dry sand.

"Certainly there's going to be a lot of impact, but I don't know if it's going to be significant impact," said Crozier, the longtime head of the Dauphin Island Sea Lab. He favors letting the buried oil remain where it is: buried.

Tony Kennon is worried about a different type of impact – the loss of tourist dollars if there's another oil-stained season in Orange Beach, where he serves as mayor. People don't like the idea of an oily beach, even if they can't see the pollution, he said, and a hurricane could easily expose buried oil deposits, creating a new wave of concern.

Business was off about 50 percent this year because the spill scared away tourists, and Kennon says the town's economy couldn't take another blow like that.

Kennon has given BP a deadline of New Year's Day to finish the deep-cleaning work on Orange Beach's nine miles of coast.

"If they want me to sign off on it, it's going to have to be white and squeaky clean," said Kennon. "We sell ourselves on sugar-white beaches. If we don't have that at the end of all this, we need compensation."